Java 在用户拖动鼠标时收听 JFrame 调整大小事件？
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Listen to JFrame resize events as the user drags their mouse?
提问by Clinton
When a user clicks on the corner of a JFrame to resize and drags the mouse around, the JFrame redraws based on the current position of the mouse as the user drags. How can you listen to these events?
当用户单击 JFrame 的角以调整大小并四处拖动鼠标时，JFrame 会在用户拖动时根据鼠标的当前位置重新绘制。你怎么能听到这些事件？
Below is the what I have currently tried:
以下是我目前尝试过的：
public final class TestFrame extends JFrame {
public TestFrame() {
this.addComponentListener(new ComponentAdapter() {
public void componentResized(ComponentEvent e) {
// This is only called when the user releases the mouse button.
System.out.println("componentResized");
}
});
}
// These methods do not appear to be called at all when a JFrame
// is being resized.
@Override
public void setSize(int width, int height) {
System.out.println("setSize");
}
@Override
public void setBounds(Rectangle r) {
System.out.println("setBounds A");
}
@Override
public void setBounds(int x, int y, int width, int height) {
System.out.println("setBounds B");
}
}
How can I determine and constrain how the user resizes a window (based on the current aspect ratio of the window) as they are dragging around the mouse around?
当用户在鼠标周围拖动时，如何确定和限制用户如何调整窗口大小（基于窗口的当前纵横比）？
采纳答案by Tom Hawtin - tackline
You probably need to override something like validate(don't forget to call the super). Of course, that still may not work if you are using a windowing system to configured to drag outlines.
您可能需要覆盖类似的东西validate（不要忘记调用超级）。当然，如果您使用窗口系统配置为拖动轮廓，那仍然可能不起作用。
回答by Alex Ntousias
You can add a component listener and implement the componentResized function like that:
您可以添加一个组件侦听器并像这样实现 componentResized 函数：
JFrame component = new JFrame("My Frame");
component.addComponentListener(new ComponentAdapter()
{
public void componentResized(ComponentEvent evt) {
Component c = (Component)evt.getSource();
//........
}
});
EDIT:Apparently, for JFrame, the componentResized event is hooked to the mouseReleased event. That's why the method is invoked when the mouse button is released.
编辑：显然，对于 JFrame，componentResized 事件与 mouseReleased 事件挂钩。这就是为什么在释放鼠标按钮时调用该方法的原因。
One way to achieve what you want, is to add a JPanel that will cover the whole area of your JFrame. Then add the componentListener to the JPanel (componentResized for JPanel is called even while your mouse is still dragging). When your frame is resized, your panel will also be resized too.
实现您想要的一种方法是添加一个 JPanel，它将覆盖 JFrame 的整个区域。然后将 componentListener 添加到 JPanel（即使鼠标仍在拖动，也会调用 JPanel 的 componentResized）。当您的框架调整大小时，您的面板也将调整大小。
I know, this isn't the most elegant solution, but it works!
我知道，这不是最优雅的解决方案，但它有效！
回答by Pyadav
public class MouseDrag extends Component implements MouseListener,
MouseMotionListener {
/** The Image we are to paint */
Image curImage;
/** Kludge for showStatus */
static Label status;
/** true if we are in drag */
boolean inDrag = false;
/** starting location of a drag */
int startX = -1, startY = -1;
/** current location of a drag */
int curX = -1, curY = -1;
// "main" method
public static void main(String[] av) {
JFrame f = new JFrame("Mouse Dragger");
Container cp = f.getContentPane();
if (av.length < 1) {
System.err.println("Usage: MouseDrag imagefile");
System.exit(1);
}
Image im = Toolkit.getDefaultToolkit().getImage(av[0]);
// create a MouseDrag object
MouseDrag j = new MouseDrag(im);
cp.setLayout(new BorderLayout());
cp.add(BorderLayout.NORTH, new Label(
"Hello, and welcome to the world of Java"));
cp.add(BorderLayout.CENTER, j);
cp.add(BorderLayout.SOUTH, status = new Label());
status.setSize(f.getSize().width, status.getSize().height);
f.pack();
f.setVisible(true);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
// "Constructor" - creates the object
public MouseDrag(Image i) {
super();
curImage = i;
setSize(300, 200);
addMouseListener(this);
addMouseMotionListener(this);
}
public void showStatus(String s) {
status.setText(s);
}
// Five methods from MouseListener:
/** Called when the mouse has been clicked on a component. */
public void mouseClicked(MouseEvent e) {
}
/** Called when the mouse enters a component. */
public void mouseEntered(MouseEvent e) {
}
/** Called when the mouse exits a component. */
public void mouseExited(MouseEvent e) {
}
// And two methods from MouseMotionListener:
public void mouseDragged(MouseEvent e) {
Point p = e.getPoint();
// System.err.println("mouse drag to " + p);
showStatus("mouse Dragged to " + p);
curX = p.x;
curY = p.y;
if (inDrag) {
repaint();
}
}
public void paint(Graphics g) {
int w = curX - startX, h = curY - startY;
Dimension d = getSize();
g.drawImage(curImage, 0, 0, d.width, d.height, this);
if (startX < 0 || startY < 0)
return;
System.err.println("paint:drawRect @[" + startX + "," + startY
+ "] size " + w + "x" + h);
g.setColor(Color.red);
g.fillRect(startX, startY, w, h);
}
}
回答by vaughandroid
Another workaround (which is very similar to Alex's but a little more straightforward) is to listen to the events from the JFrame's root pane instead:
另一种解决方法（与 Alex 的非常相似，但更直接一些）是从JFrame的根窗格中监听事件：
public final class TestFrame extends JFrame {
public TestFrame() {
this.getRootPane().addComponentListener(new ComponentAdapter() {
public void componentResized(ComponentEvent e) {
// This is only called when the user releases the mouse button.
System.out.println("componentResized");
}
});
}
}
Depending on other implementation details, it's possible that the root pane might be changed. If that's a possibility then you could override setRootPane()and deal with that. Since setRootPane()is protected and only called from the constructor though, it's unlikely you'll need to do that.
根据其他实现细节，根窗格可能会更改。如果有这种可能性，那么您可以覆盖setRootPane()并处理它。由于setRootPane()受保护并且仅从构造函数调用，因此您不太可能需要这样做。
